Hydraulic actuator



March 25, 1952 K. J. ALwARD 2,590,144 I HYDRAULIC ACTUATOR Filed Aug. 14, 1948 2 sl-xEETs-SHEET 2 IN VEN TOR. Kfm/v5 7H JAL wAeo.

@lana/M ATTORNEYS stood in the art.

Patented Mar. 25, 1952 UNITED STATES PATENT OFFICE HYDRAULIC ACTA-TOR Kenneth J .-Alward, South Bend, Ind.

Application August 14, 1948, SerialNo. 44,265

(Cl. S04-54.6)

-2 Claims. l

This invention relates to improvements in hydraulic actuators, and more particularly to a device 'for 4operating the hydraulic brakes of automobiles and trucks. y

The primary object of the invention is to provide Aa device Tfor multiplying Vby leverage Vthe fforce applied by a .brake pedal or other actuator in order to obtain 'a high value of viluid displacement and Huid pressure l'from a small actuating movement l-e'ifected through 'the 'application to the pedal Vor other actuator vof a small actuating pressure.

A further Objectis to provide `a device of this character -wherein two master cylinders are employed yand an actuator is pivotally connected thereto -atspaced points so that the actuator has `a floating vmovement and action and its 'fulcrum is free lto change from the point ofconnection -thereof with one master cylinder "to the point 'of connection thereof with the other master cylinder during its operating stroke as the resist- `ances fof the master cylinders vary in use.

Other objects will be apparent from the following specification.

lIn. lthe 'drawing lFig. l is aside View of the device with parts shown in section illustrating in dotted lines 'the initial movement oi the lbrake pedal or other actuator from its resting position.

Fig. 2 illustrates the position assumed by the parts upon further movement of the pedal from the dotted line position shown vin Fig. 1.

Fig. 3 is a view .illustrating van alternative embodiment of the invention.

Referring to the drawings, and particularly to Figs. 1 and 2 thereof, the numeral I6 Ydesignates a master cylinder and the numeral I2 a second master cylinder. The cylinders Ill and 'I2 are suitably mounted upon 'the frame of an automotive vehicle or 'truck in the manner well under- The numeral I4 designates a foot pedal although it will be understood that any other type of actuator may be employed. The foot pedal has a foot plate I6 at its upper end and 'is `pivotally connected -at lI8 to the master cylinder vIII `and at 20 to 'the master cylinder I2. The pedal or other actuator 'is normally `urged to the ffull lline 'position illustrated in Fig. l by a spring'22.

Each of the master cylinders may be of any conventional construction and is of rthe `character well understood in the art. As illustrated herein, each of the cylinders comprises -a housing 24 having a cylindrical bore 26 therein .and a r-eservoir chamber 28, said cylinder and chamber being separated by a wall which is provided with one 'or more ports establishing communication :between the Acylinder and the chamber and including the .pressure compensating port 32. The rhousing 24 is preferably constructed to have two ror more ports therein. As here illustrated, these housings may have a port 34 at one end thereof and a port in its top adapted to be closed by a plug 36, as herein shown in Fig. 1 with respect to cylinder I0.

vA piston'spool 38 Vis mounted in the cylinder 26 and is provided a'tits inner end with an enlarged portion mounting 'a seal 40 which is preferably 'cup-shaped to be sealed upon application of pres- 'sure at its concave 'face and to permit reverse flow of liquid therepast. A coil spring 42 bears against the inner end of the piston at one end and against the housing at its opposite end. A port 44 is formed in one end of the cylinder facing the end of the piston spool which mounts the seal 46. The opposite or outer end of the spool 38 is enlarged `and mounts a seal 46. The .pi'stonspool has a stem 48 which projects through an opening in an end cap closing the end of the cylinder. A-clevs 52 is mounted on the outer V 'ing at one end against the cap 5B. The opposite tended fully and the stop 55 will be positioned spaced .from the clevis '52. The master cylinder 'I 2 is illustrated as provided with a collapsible vbellows 56 encircling the stem 48 and connected at its opposite ends to the cap 5!) and the clevis 52. The pivot point I8 may constitute a pin connecting the clevis 52 of the cylinder unit I0 to the pedal I4 or other actuator, and the pivot 2l) may constitutea pivot pin connecting the clevis 52 of the cylinder I2 to the pedal.

A conduit 6l] iis connected at one end to the outlet port 44 of the cylinder chamber 26 of the cylinder unit Il), and a conduit 62 is connected to the voutlet port 44 of the cylinder unit I2. The conduit `62 is `connected with a check valve 64, and a conduit 66 leads from said check valve.

The conduit 66 communicates with the conduit 66' at a junction 68. The port 34 of the reservoir chamber l128 of the `cylinder unit I0 is connected by conduit 'I0 with the reservoir chamber v2li of the cylinder unit I2.

In the connection and arrangement of the parts, the positioning relation between the pivots I8 and 28 and the length of the pedal I4 is important. Thus it will be observed that the spacing between the pivots I8 and 20 is less than the spacing between the foot plate I6 and the pivot I8. The ratios between these dimensions is so correlated with the resistances of the two cylinder units I and I2 and of the spring 22 that when force is applied to the pedal or other actuator I4, as at the foot plate I5, that pedal or actuator is first caused to move from the full line position to the dotted line position in Fig. 1. For this purpose, the master cylinder I2 is selected t0 have a greater inherent resistance than the master cylinder I0. Consequently, during this initial movement, the pivot point 28 serves as the fulcrum of the pedal or other actuator because of this resistance ratio and because the spacing between the pivots I8 and 28 is less than the spacing between pivot I8 and the foot plate I6. The movement of the pedal to the dotted line position in Fig. l continues until the seal of the piston 38 passes and closes the compensating port 32 between the cylinder bore and the reservoir chamber 28 of the unit I8. At this position, the clevis abuts the stop 55, so that the resistance of spring 54 is first brought into play.

Thereafter, continued movement of the actuator in the same direction will cause the pedal or actuator I4 to pivot about the point I8 as a fulcrum by reason of the fact that the resistance of spring 54 added to the inherent resistance of cylinder IU produces a total resistance greater than the inherent resistance of cylinder I2. The resultant actuation of the piston of the cylinder I2 will force fluid from that cylinder into a uid pressure line and past the check valve 64 for movement into the pressure responsive cylinders (not shown) for actuating the wheel brakes (not shown) Continued movement of the brake pedal to increase the pressure applied at the wheel brakes proceeds with the pivot I8 as a fulcrum until the resistance of the cylinder unit I2 increases to a value exceeding the value of the combined resistance of the spring 54 and the cylinder unit I0 in the leverage system, whereupon the fulcrum of the pedal or other actuator is transferred to the pin 20, and continued pedal operation or depression causes the piston 33 of the cylinder unit I8 to be further actuated. As the latter action occurs, fluid expelled from the unit I and passing through the conduit 68 is directed through the line 85 to the brakes by virtue of the interposition of the check valve 8A between the junction 88 of the conduits 88 and 68 and the outlet port 441 of the cylinder unit I2. Inasinuch as the master cylinder I8 has a high leverage ratio, it is capable of producing high hydraulic pressures upon the application of a minimum amount of force upon the actuator or pedal I4.

As soon as the actuating force is released from the foot pedal or other actuator, the pull of the return spring 22 coupled with the action of the springs of all of the hydraulic units, such as the springs 42 and 54, acts to return the actuator to the full line position shown in Fig. 1. Upon return of the pedal to its normal or inoperative position the compensating ports 32 of the two cylinder units are uncovered to reestablish communication between the reservoirs'28 and the cylinder bores 26 of said units. In this connection it will be observed, however, that ow in the system cannot occur directly from line 66 into the cylinder unit I2 because of the interposed check valve 64. Therefore, the initial flow upon return extends through the conduit 60 into the cylinder bore 25 of the cylinder unit Il). When the compensating port 32 of this cylinder unit is opened, the liquid may ow therethrough into the reservoir 28 of the unit I0 and thence through the conduit III into the reservoir 28 of the cylinder unit I2.

The embodiment illustrated in Fig. 3 employs parts of substantially the same construction above described, and similar parts bear the same reference numerals. In this embodiment the clevis 52 of the cylinder unit II! is pivotally connected at IB at one end of a rigid lever or link 88 whose opposite end is pivoted at 28 to the clevis 52 of the cylinder unit I2. At substantially the mid-point 82 of said link the return spring 22 is connected thereto to pull upon the same in a direction t0 move the pistons of the two piston units to their inoperative or normal position illustrated in Fig. 1. The actuator 84, which may be connected to a foot pedal or any other suitable device which is adapted to move in the direction of the arrow upon movement from its normal or inoperative position, has a clevis 86 mounted thereon which is pivotaly connected to the link at 88. As here illustrated, spacing between the pivot points 52 and S8 is less than the spacing between the pivot points 28 and 88.

The arrangement of spring 54 upon the piston stem of cylinder I8, arranged for that limited stem movement which is necessary to close the compensating port 32 before the compression of said spring commences, is used in this embodiment also. The sequence of operation of the cylinder units II) and I2 during movement of the actuator in the direction of the arrow is the same as that described above. More specically, the initial movement of the actuator 84 causes the link 88 to swing about the pivot 20 as a fulcrum until the movement of the piston of the cylinder unit I8 has closed the compensating port 32 therein and the compression of spring 54 commences. Thereafter, when the resistance of the cylinder IE! is increased due to the fact that the resistance of spring 54 comes into play, the lever is caused to ulcrum about pivot point I8 to permit actuation of the piston of the cylinder unit I2. Subsequent operation in actuating direction causes the fulcrum point of the link 80 to change from one to the other of the two pivot points I8 and 2D as the resistances of the cylinder units vary one relative to the other.

In both forms of the device illustrated, the same advantages of a iloating action nding its own fulcrum as the resistance values of the actuated parts vary, and of the increase in the fluid pressure applicable per unit of movement of the actuator, are realized. In other words, the principle of operation of the two embodiments is the same, and in each the pressure required to be applied manually to the actuator to achieve a given braking result is reduced, compared to the pressure required to actuate previous brake operating devices. Likewise, the stroke o1 the pedal or other actuator is reduced, compared to the stroke of other actuating devices.

While the preferred embodiments of the invention have been illustrated and described herein, it will be understood that changes may be made in the construction within the scope of the appended claims without departing from the spirit of the invention.

I claim: I

l. A brake operating device comprising a pair of master cylinder units each having a cylinder, a piston reciprocable therein and a reservoir cornmunicating with the cylinder through a compensating port while the piston is at an inoperative position; a pair of pressure outlet lines connected with said cylinders and with a pressure transmitting line; an actuator including a rigid member spring-urged to inoperative position and pivotally connected at spacedv points to said pistons and having a point of pressure application unequally spaced from said pivot connections Whereby pressure is applied to said pistons unequally, said actuator including an elongated member having actuating pressure applied at one end thereof and said pivot connections at its opposite end spaced apart" longitudinally a distance less than the spacing of the inner pivotal connection from the pressure applying end thereof.

2. A brake operating device comprising a pair of master cylinder units each having a cylinder, a piston reciprocable therein and a reservoir communicating with the cylinder through a com- .pensating port while the piston is at an inoperative position; a pair of pressure outlet lines connected with said cylinders and with ,a pressure transmitting line; an actuator including a rigid member spring-urged to inoperative position and pivotally connected at spaced points to said pistons and having a point of pressure application unequally spaced from said pivot connections whereby pressure is applied to said pistons unequally. said actuator constituting a foot pedal. said units being adapted to be xedly mounted and said pivot connections between said pedal and units forming the sole support of said pedal whereby the fulcrum of the pedal will depend upon the relative resistances of said units at all points throughout the stroke of the pedal.

KENNETH J. ALWARQ.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,828,679 Pieper Oct. 20, 1931 1,921,008 Shinn Aug. 8, 1933 2,247,827 Wegmann July 1, 1941 2,263,263 Dodge Nov. 18, 1941 2,328,685 Schnell Sept. 7, 1943 2,341,318 Forbes Feb. 8, 1944 FOREIGN PATENTS Number Country Date 348,691 Great Britain May 15, 1931 782,865 France Mar. 25, 1935 

